Tandem sheave stringing block



R. CRONKRIGHT 3,012,756 TANDEM SHEAVEI STRINGING BLOCK Dec. 12, 1961 Filed July 51, 1959 2 Sheets-Sheet 1 Dec. 12, 1961 R. CRONKRIGHT TANDEM SHEAVE STRINGING BLOCK 2 Sheets-Sheet 2 Filed July 51, 1959 //v VAC/V701? CPa/ww/awf United States Patent O 3,012,756 TANDEM SHEAVE STRINGING BLOCK Russell Cronkright, P.O. Box 7766, Denver 15, Colo. Filed July 31, 1959, Ser. No. 830,776 15 Claims. (Cl. 254-1343) This invention relates to stringing block apparatus and more particularly to tandem sheave stringing block apparatus.

Most of the conventional stringing block devices used in stringing conductor are of the single sheave type. It has been found that the use of the single sheave block often times results in damage to the cable during the stringing operation. It has also been found that when the single sheave type is employed, especially in the conditions of sag tensions, the cable tends to deform due to the bending moments of the cable. The single sheave of blocks also have a tendency to resist passing of spliced sleeves and often times become disaligned with the cable during the stringing operation. Heretofore one manner of overcoming these problems was to employ a rather large single pulley or sheave which resulted in a heavy and bulky structure.

Another disadvantage experienced stringing blocks is in the time lost during installation and removal. It was also found that the large single sheave blocks could not be grouped in side by side relation upon the stringing supports which, of course, resulted in loss of time during reconductoring stringing.

During the stringing operation the stringing block is usually suspended from an insulator and the cable is thereafter threaded through the block by lead lines. After the cable is secured in place, the stringing block is removed. The conventional stringing blocks do not permit installation of armor rods while the cable is positioned within the block.

Conventional stringing blocks are ordinarily suspended from an insulator and especially designed blocks are required for mounting the blocks upon cross arms or insulators.

Myinvention is directed to overcome these problems.

An object of this invention is to provide a novel tandem sheave stringing block, of simple and inexpensive construction, for use in stringing cable or the like.

Another object of this invention is to provide a novel stringing block apparatus for use in stringing cable including a shiftable pulley-supporting frame for supporting a pulley structure and shiftable from a closed to open position and constructed to retain a cable positioned upon the pulley structure when in the open condition.

Another object of this invention is to provide a novel and improved tandem sheave stringing block apparatus including a releasable and shiftable frame shiftable from an open to a closed position and arranged and constructed to retain a cable positioned on the tandem sheave against lateral displacement when the frame is in the open condition.

A further object of this invention is to provide a novel mounting adaptor for use in mounting a stringing block on a support such as an insulator or cross arm.

A still more specific object of this invention is the proin conventionalvision of a tandem sheave stringing block in combination 1 with a mounting adaptor arranged and constructed to be positioned upon and secured to a support such as a cross arm or an insulator.

These and other objects and advantages of this invention will more fully appear from the following description, made in connection with the accompanying drawings, wherein like reference characters refer to the same or similar parts throughout the several views, and in which:

FIG. 1 is a side elevational view of a plurality of power "ice line supports utilizing my novel tandem sheave stringing block during the stringing operation;

FIG. 2 is a side elevational view of the novel tandem sheave stringing block attached to an insulator and supporting a cable thereupon with certain parts thereof broken away and with the cable shown in sagged condition by dotted line configuration;

FIG. 3 is an end elevational view of my novel tandem sheave stringing block with parts thereof broken away and shown in inoperative position by dotted line configuration;

FIG. 4 is a side elevational view of the tandem sheave stringing block in a canted position;

FIG. 5 is a side elevational view of my novel mounting adaptor indicating the manner of mounting the tandem sheave stringing block upon an insulator;

FIG. 6 is an end elevational view of the mounting adaptor and tandem sheave stringing block shown in FIG. 5;

FIG. 7 is a side elevational view of my mounting adaptor indicating the manner of mounting the tandem sheave stringing block on a cross arm structure; 7

- FIG. 8 is an end elevational view of the adaptor and tandem sheave stringing block shown in FIG. 7; and

FIG. 9 is an enlarged perspective view of a part of the novel mounting adaptor.

Referring now to the drawings, FIG. 1 indicates a manner in which my novel tandem sheave stringing block is used during the stringing operation of an overhead cable C prior to its attachment to a conventional insulator structure which in turn is supported by a power line support tower T. Referring now to FIG. 2, it will be seen that the socket type suspension insulator 10 is provided with a conventional ball fitting 11 to which is suspended my novel tandem sheave stringing block generally designated 12. Tandem sheave block 12 includes a shiftable and releasable frame structure 13. Shiftable frame struc ture 13 includes a pair of rigid plates 14 and 15 connectedtogether in fixed parallel relation by a spacer bolt 16. Plates 14 and 15 are preferably formed of steel plate and it will be noted that each plate is of substantially tri angular shape.

A pair of pulleys 17 are positioned between the plates 14 and 15 and are arranged in tandem relation with their respective axles 18 secured to the plates adjacent the lower portions thereof. Pulleys 17 are preferably formed of diecast aluminum alloy and rotate about their respective axles 18. Although not shown in the drawings, each of the pulleys or sheaves 17 may be provided with needle type roller bearings which, of course, reduce friction loads. Referring now to FIG. 3, it will be seen that pulleys 17 are grooved as at 19 to provide proper seating of cable C during the stringing operation.

A mounting bracket 20 is hingedly connected as at 21 to plate 14 and permits lateral shifting or swingingof frame 13 from a closed position to an open position as in FIG. 3. Mounting bracket 20 is provided with an opening 22 which receives an elongated cylindrical locking member 23 therein. Locking member 23 is positioned within opening 22 for rotative movement relative thereto and is also mounted for limited axial shifting.

3, it Will be seen that one end of locking member 23 is provided with a key 24 extend- Plate 15 as seen in FIG. 4 is provided with an aperture 25 of keyhole configuration and receives the keyed end of locking member 23 therein. The other end of locking member 23 is provided with a counter weight pin 26 which serves to maintain locking member 23 against rotative movement when in the is provided with a socket type fitting 28 integrally formed therewith. Socket 28 is adapted to be secured to insulator fitting 11 in a conventional and well known manner.

Referring now to FIG. 3, the tandem sheave stringing block 12 is shown in closed position in full line configuration and is shown in open position in dotted line configuration. It will be noted that plate 15 extends upwardly beyond the upper circumferential surface of pulleys 17 and is in overlapped relation with bracket 20 when the stringing block is in closed position. It will also be noted that hinge 21 is positioned above the upper circumferential surfaces of pulleys 17 so that plates 14 and 15 extend upwardly and beyond the upper circumfer ential surfaces of the respective pulleys at all times. This relationship of the plates 14 and 15 to pulleys 17 prevents lateral displacement of the cable when the shiftable frame 14 is in the open position as is clearly seen in dotted line configurationin FIG. 3. i

The sleeve 27 permits fore and aft rocking or canting of the stringing block so that the pulleys 17 are in constant alignment with cable C as shown in FIG. 4. This constant alignment feature dampens momentary stress loads when, for example, a splice connection is passed through the stringing block.

Another novel feature of my invention is shown in FIGS. through 9 and includes means for mounting the tandem sheave block upon an insulator or directly upon a cross arm. Referring now to FIGS. 5, 6 and 9, the tandem sheave stringing block 12 is shown mounted upon an insulator 40 by my novel mounting adaptor 41. Insulator 40 is provided with a conventional groove 40a and has its upper portion flanged as at 40b. My novel adaptor as used to effect this mounting includes a pair of V-shaped straps 42 rigidly secured to a base plate 43 and disposed in substantially parallel relation.

When the mountingadaptor 41 is used to mount stringing block 12 upon an insulator, spacer bolt 16 is removed and frame 13 is positioned between straps 42. The apex of straps 42 are provided with openings and a bolt 44 is passed through the openings and provides a means for securing the stringing block to the adaptor. Referring now to FIG. 6, it will be seen that bolt 44 is provided with a sleeve which permits straps 42 to be maintained in spaced relation whereby bolt 44 may be cinched up tight by a conventional locking nut. The openings in plates 14 and 15 are somewhat larger than sleeve 45 so that stringing block 12is permitted to rock in a fore and aft direction. Straps 42 are provided with stops 42a which limit the oscillating or fore and aft rocking of the stringing block 12 but are sufficiently spaced below the lower edges of frame 13 so that sufficient rocking is possible to thereby permit proper alignment of the pulleys or sheaves 17 with the cable.

.The means for securing adaptor 41 to insulator 40 include. a semi-cylindrical member 46 which is secured to the under side of base plate 43. Semi-cylindrical member 46 is provided with a pair of threaded lugs 47 which pass through apertures formed in base plate 43 and are locked thereto by locking nuts 48. Angle members 49 are secured to opposite ends of semi-cylindrical member 46 as by welding or the like and a slot 50 is formed in one. leg of'each of the angle members. It will be noted that slots 50 are each formed in a leg of each angle member 49 disposed on opposite longitudinal sides of semi-cylindrical member 46 and that-the other leg of each ofthe angle members has a chain strap 51 secured thereto; Each of the chain straps 51 is provided with a threaded member 52 at its outer end and which carries a wing nut 53. A flexible sleeve 54 is positioned around chain strap 51 and may be formed of rubber material orthe like.

Referring now to FIGS. 5 and 6, the manner of attach-' ing adaptor 41 to insulator 40 will now be described. T

Semi-cylindricalmernber 46 is positioned within groove 40a of insulator 40 and the straps 51- are pulled around 4 the outer circumferential surfaces of insulator 40 and positioned against flange 40b. The threaded ends 52 are thereafter positioned in slots and the wing nuts 53 are tightened to thereby tighten straps 51 in place. Sleeves 54 function to prevent scoring or marring of the insulat tor 40. 7

Referring now to FIGS. 7 and 8, the novel adaptor 41 is shown mounting stringing block 12 upon a cross arm A. When mounting the stringing block 12 upon a cross arm in this manner, the semi-cylindrical member is re moved and base plate 43 is positioned upon the upper surface of the cross arm. A pair of bolts 55 are passed through the apertures in base plate 43 and also pass through registering openings in a clamping element 5.6 placed against the lower surface of cross arm A. The lower ends of bolts 55 are threaded and locking nuts 57 secure clamping element 56 in locked relation against the lower surface of cross arm A.

During the stringing operation the tandem sheave stringing block 12 is first secured to an insulator 10' as shown in FIGS. 1-4 of the drawings. The cable C Which is mounted on a reel is thereafter threaded through the stringing block as for example by lead lines until the entire length of cable is positioned in place. The outer end of the cable is secured to the fitting of the support and the intermediate portions of the cable are thereafter secured to their respective fittings. The'blocks are removed and the entire stringing operation can be accomplished in a relatively short time.

Referring now to FIGS. 2 and 4, it will be seen that plates 14 and 15 are each provided with an opening to thereby permit the cable to be marked for the installation of rods or suspension clamps.

In some instances it is preferable to install armor rods while the conductor is in the block and this may be accomplished by releasing locking member 23 from plate 15 and permitting the shiftable frame 13 to shift to the open position. This permits ready access to the cable and plates 14 and 15 retain the cable against displacement during this operation. This is especially true when the cable is subjected to up strain whereby the cable has a tendency to be displaced laterally ofthe pulleys and dumped therefrom. I

Referring now to FIG. 2, the cable is shown in sagged condition by dotted line configuration. The upper circumferential surfaces of the sheaves or pulleys 17, as it will be seen, substantially reduce the bending moment of the cable. It has been found that the bending moment Will be reduced to one half when the angle defined by the cable and a common tangential plane of the pulleys is 60 or less. This reduction of the bending moment greatly lessens damage to the cable due to load stresses.

It will also be noted from FIG. 3 that the'overall width of the tandem sheave stringing block is less than the width of the insulators. This slim design permits grouping of the blocks in side by side relation upon a single support. This side by side arrangement can not be obtained with conventional stringing blocks due to their inherent bulky construction.

The novel adaptor, of course, permits versatilityof use of my novel tandem sheave stringing block and the adaptor is arranged and constructed for ready attachment .to an insulator or'cross arm with a minimum loss of time.

'It willbe seen from the foregoing description that I have provided a novel tandem sheave stringing block which may be readily attached and removed from a support such as an insulator or the like. It will also be noted from the foregoing description that 11 have provided a novel tandem sheave stringing block which permits equal distribution of-the weight of a cable thereupon and which is arranged and constructed to be maintained in constant alignment with thecable during thestringing operation; It will also be seen from the preceding description that I have provided a novel stringing block apparatus which permits: installing armorrods" while the cable is positioned upon the pulleys and which is constructed to prevent dumping or displacement of the cable during this installation process.

It will also be noted from the foregoing description that I have provided a novel tandem sheave stringing block which includes a shiftable and releasable frame which may be positively locked in closed position without any danger of becoming inadvertently unlocked.

It will also be noted from the foregoing description that I'have provided a novel mounting adaptor for use in combination with my novel tandem sheave stringing block which permits ready attachment of the stringing block to various supports such as a cross arm or insulator.

These overall advantages permit quick and eflicient installation of conductor cables with a minimum of time loss and with the danger of damage to the cable greatly minimized.

It will, of course, be understood that various changes may be made in the form, details, arrangement and proportions of theparts without departing from the scope of'this invention which consists of the matter shown and described herein and set forth in the appended claims.

What is claimed is: a I v 1. Stringing block apparatus for use in stringing cable comprising a releasable .and vshiftable frame structure including a pair of rigid plates connected in fixed spaced relation, pulley structure positioned between and mounted to said plates, a mounting bracket having means for attachment to a support such as an insulator and being hingedly connected to the upper portion of one of said plates to thereby permit said frame structure to shift from a closed position to an open position, said hinge connection being positioned above the upper circumferential surface of said pulley structure, the other of said plates extending upwardly into overlapped relation to said mounting bracket when said frame is in the closed position whereby said plates extend upwardly and beyond the upper circumferential surface of said pulley structure at all times, locking means releasably interlocking said bracket and frame structure in closed position and being releasable to permit shifting of said frame structure to open position, said locking means defining a pivotal connection between said bracket and frame structure to permit pivoting of the latter about an axis extending substantially parallel to the axis of rotation of said pulley construction and said plates serving to restrain a cable positioned upon said pulleys against lateral displacement when said frame structure is shifted into an open position.

2. Tandem sheave stringing block for use in stringing cable comprising a releasable and shiftable frame structure including a pair of rigid plates connected in fixed spaced relation, a pair of pulleys disposed in tandem relation and positioned between and rotatably mounted to said plates, a mounting bracket having means for attachment to a support such as an insulator and being hingedly connected to the upper portion of one of said plates to thereby permit said frame structure to shift from a closed position to an open position, said hinge connection being positioned above the upper circumferential surface of said pulleys, the other of said plates extending upwardly into overlapped relation to said mounting bracket when said frame is in the closed position whereby said plates extend upwardly and beyond the upper circumferential surface of said pulleys at all times, locking means for releasably interlocking said bracket and frame leasable to permit shifting of said frame structure in open position, and said plates serving to restrain a cable positioned upon said pulleys against lateral displacement when said frame structure is shifted into 3. Tandem sheave stringing block apparatus for use in stringing cable comprising a releasable and shiftable frame structure including a pair of rigid plates connected in fixed parallel relation, a pair of pulleys disposed structure in closed position and reopen position.

in tandem relation and positioned between and mounted to said plates, a mounting bracket having means for attachment to a support and being hingedly connected to the upper portion of one of said plates to thereby permit said frame structure to shift from a closed to open position, said hinge connection being positioned above the upper circumferential surface of said pulleys, the other of said plates extending upwardly into overlapped relation to said mounting bracket when said frame is in the closed position whereby said plates extend upwardly and beyond the upper circumferential surfaces of said pulleys at all times, locking means carried by said mounting bracket and engageable with said other plate member for releasably interlocking said frame structure to said bracket in the closed position and releasable to permit shifting of said frame structure to open position, said locking mechanism defining a pivotal connection between said bracket and frame structure to permit pivoting of the latter about an axis extending substantially parallel to the axes of rotation of said pulleys.

4. Tandem sheave stringing block for use in stringing cable comprising a releasable shiftable frame structure including a pair of rigid plates connected in fixed parallel relation, a pair of pulleys disposed in tandem relation and positioned between and mounted to said plates, a mounting bracket having means for attachment to a support such as an insulator and being hingedly connected to the upper portion of one of said plates to thereby permit said frame structure to shift from an open to a closed position, locking means for releasably interlocking said frame structure and bracket in closed position and including an elongate cylindrical member rotatably mounted on said bracket, said elongate member being axially shiftable relative to said bracket and engaging said other plate for retaining said frame structure in closed position, and said frame structure being releasable from closed position upon rotation and axial shifting of said member.

5. The structure as defined in claim 4 wherein said elongate member is provided with an element extending radially from one end thereof and said other plate is provided with a keyhole shaped opening for receiving and retaining said one end of the elongate member when the frame is in closed position.

6. Tandem sheave stringing block for use in stringing cable comprising a frame structure including a pair of rigid plates connected in fixed spaced relation, a pair of pulleys disposed in tandem relation and positioned between and rotatably mounted to said plates, a mounting adaptor including a base member having a pair of opposed straps secured thereto, said base member having securing means releasably securing said base member upon a support such as an insulator, said straps extending upwardly from said base member and being arranged in substantially parallel relation to said rigid plates and having means interconnecting the upper portions thereof, and said interconnecting means serving to pivotally support said stringing block frame structure between said strapsfor fore and aft oscillating movement relative thereto.

7. The structure as defined in claim 6 and one of said straps is provided with stop means for limiting oscillating movement of said frame structure.

8. Mounting adaptor apparatus for use in mounting a cable stringing block upon a support such as a pintype upper portions thereof, and said interconnecting means pivotally supporting a cable stringing block between said straps.

9. The structure as defined in claim 8 wherein one of said straps is provided with stop means limiting the pivotal movement of said stringing block when supported by said interconnecting means.

10. The structure as defined in claim 8 wherein said straps are of inverted V-shaped configuration and said base member comprises a substantially flat plate,

a 111. The structure as defined in claim 8 wherein said interconnecting means is adjustable to adjust the spacing between the upper portions of said straps.

12.- The structure as defined in claim 8 wherein said securing means includes a pair of adjustable flexible members positionable around an insulator.

-13. Mounting apparatus for use in mounting a cable stringing block to a support such as a cross arm comprising a frame, said frame including a base member having a pair of inverted V-shaped straps secured thereto, said base member having securing means releasably and rigidly securing said plate member upon a support, said straps being disposed in substantially parallel relation and extending upwardly from said plate member, means interconnecting upper portions of said straps for pivotally supporting a cable stringing block between said straps.

14. The structure asdefined in claim 13 wherein said locking means includes a clamping element secured to l5. Mounting adaptor apparatus for use in mounting a cable stringing block upon a pin-type insulator of the type having a groove formed in the upper portion thereor, said apparatus comprising a frame including a base member, a pair of opposed, spaced-apart straps fixedly secured to said base member and extending upwardly therefrom, means interconnecting the uppermost portion of said straps and defining a pivot connection for pivotal- 'ly supporting a cable stringing block disposed between said base member for clamping against the under surface v of a cross arm support.

said straps, positioning means on said base engageable within the grooved portion of a pin-type insulator, and a pair of elongate flexible members connected to said base member and being adjustable for releasably engaging a pin-type insulator for releasably securing said adaptor apparatus in superimposed relation upon the latter.

References Cited in the file of this patent UNITED STATES PATENTS 

